<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
 <head>
  <meta http-equiv="content-type" content="text/html; charset=UTF-8">
  <title>返回参数列表的某一项</title>
 </head>
 <body class="docs"><div id="layout">
  <div id="layout-content"><div id="function.func-get-arg" class="refentry">
 <div class="refnamediv">
  <h1 class="refname">func_get_arg</h1>
  <p class="verinfo">(PHP 4, PHP 5, PHP 7)</p><p class="refpurpose"><span class="refname">func_get_arg</span> &mdash; <span class="dc-title">返回参数列表的某一项</span></p>

 </div>
 
 <div class="refsect1 description" id="refsect1-function.func-get-arg-description">
  <h3 class="title">说明</h3>
  <div class="methodsynopsis dc-description">
   <span class="methodname"><strong>func_get_arg</strong></span>
    ( <span class="methodparam"><span class="type">int</span> <code class="parameter">$arg_num</code></span>
   ) : <span class="type"><a href="language.pseudo-types.html#language.types.mixed" class="type mixed">mixed</a></span></div>

  <p class="para rdfs-comment">
   从用户自定义函数的参数列表中获取某个指定的参数。
  </p>
  <p class="para">
   该函数可以配合
   <span class="function"><a href="func_get_args.html" class="function">func_get_args()</a></span> 和 <span class="function"><a href="func_num_args.html" class="function">func_num_args()</a></span>
   一起使用，从而使得用户自定义函数可以接受自定义个数的参数列表。
  </p>
 </div>


 <div class="refsect1 parameters" id="refsect1-function.func-get-arg-parameters">
  <h3 class="title">参数</h3>
  <p class="para">
   <dl>

    
     <dt>
<code class="parameter">arg_num</code></dt>

     <dd>

      <p class="para">
       参数的偏移量。函数的参数是从0开始计数的。
      </p>
     </dd>

    
   </dl>

  </p>
 </div>


 <div class="refsect1 returnvalues" id="refsect1-function.func-get-arg-returnvalues">
  <h3 class="title">返回值</h3>
  <p class="para">
   返回指定的参数，错误则返回 <strong><code>FALSE</code></strong> 。
  </p>
 </div>


 <div class="refsect1 changelog" id="refsect1-function.func-get-arg-changelog">
  <h3 class="title">更新日志</h3>
  <p class="para">
   <table class="doctable informaltable">
    
     <thead>
      <tr>
       <th>版本</th>
       <th>说明</th>
      </tr>

     </thead>

     <tbody class="tbody">
      <tr>
       <td>5.3.0</td>
       <td>
        该函数可以在参数列表中使用。
       </td>
      </tr>

      <tr>
       <td>5.3.0</td>
       <td>
        If this function is called from the outermost scope of a file
        which has been included by calling <span class="function"><a href="include.html" class="function">include</a></span>
        or <span class="function"><a href="require.html" class="function">require</a></span> from within a function in the
        calling file, it now generates a warning and returns <strong><code>FALSE</code></strong>.
           （不知道如何翻译跟好，直接参考例2即可明白）
       </td>
      </tr>

     </tbody>
    
   </table>

  </p>
 </div>


 <div class="refsect1 errors" id="refsect1-function.func-get-arg-errors">
  <h3 class="title">错误／异常</h3>
  <p class="para">
   当在自定义函数的外面调用的该函数的时候会发出一个警告，
   或者是当 <code class="parameter">arg_num</code> 比实际传入的参数的数目大的时候也会发出一个警告。
  </p>
 </div>


 <div class="refsect1 examples" id="refsect1-function.func-get-arg-examples">
  <h3 class="title">范例</h3>
  <p class="para">
   <div class="example" id="example-6198">
    <p><strong>Example #1 <span class="function"><strong>func_get_arg()</strong></span> 例子</strong></p>
    <div class="example-contents">
<div class="phpcode"><pre><span style="color: #000000">
<span style="color: #0000BB">&lt;?php<br /></span><span style="color: #007700">function&nbsp;</span><span style="color: #0000BB">foo</span><span style="color: #007700">()<br />{<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #0000BB">$numargs&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #0000BB">func_num_args</span><span style="color: #007700">();<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;echo&nbsp;</span><span style="color: #DD0000">"Number&nbsp;of&nbsp;arguments:&nbsp;</span><span style="color: #0000BB">$numargs</span><span style="color: #DD0000">&lt;br&nbsp;/&gt;\n"</span><span style="color: #007700">;<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;if&nbsp;(</span><span style="color: #0000BB">$numargs&nbsp;</span><span style="color: #007700">&gt;=&nbsp;</span><span style="color: #0000BB">2</span><span style="color: #007700">)&nbsp;{<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;echo&nbsp;</span><span style="color: #DD0000">"Second&nbsp;argument&nbsp;is:&nbsp;"&nbsp;</span><span style="color: #007700">.&nbsp;</span><span style="color: #0000BB">func_get_arg</span><span style="color: #007700">(</span><span style="color: #0000BB">1</span><span style="color: #007700">)&nbsp;.&nbsp;</span><span style="color: #DD0000">"&lt;br&nbsp;/&gt;\n"</span><span style="color: #007700">;<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;}<br />}<br /><br /></span><span style="color: #0000BB">foo&nbsp;</span><span style="color: #007700">(</span><span style="color: #0000BB">1</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">2</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">3</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">?&gt;</span>
</span>
</pre></div>
    </div>

   </div>
  </p>
  <p class="para">
   <div class="example" id="example-6199">
    <p><strong>Example #2 <span class="function"><strong>func_get_arg()</strong></span> PHP 5.3 前后对比的例子</strong></p>
    <div class="example-contents">
<div class="phpcode"><pre><span style="color: #000000">
test.php<br /><span style="color: #0000BB">&lt;?php<br /></span><span style="color: #007700">function&nbsp;</span><span style="color: #0000BB">foo</span><span style="color: #007700">()&nbsp;{<br />&nbsp;&nbsp;&nbsp;&nbsp;include&nbsp;</span><span style="color: #DD0000">'./fga.inc'</span><span style="color: #007700">;<br />}<br /><br /></span><span style="color: #0000BB">foo</span><span style="color: #007700">(</span><span style="color: #DD0000">'First&nbsp;arg'</span><span style="color: #007700">,&nbsp;</span><span style="color: #DD0000">'Second&nbsp;arg'</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">?&gt;<br /></span><br />fga.inc<br /><span style="color: #0000BB">&lt;?php<br /><br />$arg&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #0000BB">func_get_arg</span><span style="color: #007700">(</span><span style="color: #0000BB">1</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">var_export</span><span style="color: #007700">(</span><span style="color: #0000BB">$arg</span><span style="color: #007700">);<br /><br /></span><span style="color: #0000BB">?&gt;</span>
</span>
</pre></div>
    </div>

    <div class="example-contents"><p>
     PHP 5.3 版本之前的输出：
    </p></div>
    <div class="example-contents screen">
<div class="cdata"><pre>
&#039;Second arg&#039;
</pre></div>
    </div>
    <div class="example-contents"><p>
     PHP 5.3 和之后的版本的输出:
    </p></div>
    <div class="example-contents screen">
<div class="cdata"><pre>
Warning: func_get_arg():  Called from the global scope - no function
context in /home/torben/Desktop/code/ml/fga.inc on line 3
false
</pre></div>
    </div>
   </div>
  </p>

  <p class="para">
   <div class="example" id="example-6200">
    <p><strong>Example #3 <span class="function"><strong>func_get_arg()</strong></span> example of byref and byval arguments</strong></p>
    <div class="example-contents">
<div class="phpcode"><pre><span style="color: #000000">
<span style="color: #0000BB">&lt;?php<br /></span><span style="color: #007700">function&nbsp;</span><span style="color: #0000BB">byVal</span><span style="color: #007700">(</span><span style="color: #0000BB">$arg</span><span style="color: #007700">)&nbsp;{<br />&nbsp;&nbsp;&nbsp;&nbsp;echo&nbsp;</span><span style="color: #DD0000">'As&nbsp;passed&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;:&nbsp;'</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">var_export</span><span style="color: #007700">(</span><span style="color: #0000BB">func_get_arg</span><span style="color: #007700">(</span><span style="color: #0000BB">0</span><span style="color: #007700">)),&nbsp;</span><span style="color: #0000BB">PHP_EOL</span><span style="color: #007700">;<br />&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #0000BB">$arg&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #DD0000">'baz'</span><span style="color: #007700">;<br />&nbsp;&nbsp;&nbsp;&nbsp;echo&nbsp;</span><span style="color: #DD0000">'After&nbsp;change&nbsp;&nbsp;:&nbsp;'</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">var_export</span><span style="color: #007700">(</span><span style="color: #0000BB">func_get_arg</span><span style="color: #007700">(</span><span style="color: #0000BB">0</span><span style="color: #007700">)),&nbsp;</span><span style="color: #0000BB">PHP_EOL</span><span style="color: #007700">;<br />}<br /><br />function&nbsp;</span><span style="color: #0000BB">byRef</span><span style="color: #007700">(&amp;</span><span style="color: #0000BB">$arg</span><span style="color: #007700">)&nbsp;{<br />&nbsp;&nbsp;&nbsp;&nbsp;echo&nbsp;</span><span style="color: #DD0000">'As&nbsp;passed&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;:&nbsp;'</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">var_export</span><span style="color: #007700">(</span><span style="color: #0000BB">func_get_arg</span><span style="color: #007700">(</span><span style="color: #0000BB">0</span><span style="color: #007700">)),&nbsp;</span><span style="color: #0000BB">PHP_EOL</span><span style="color: #007700">;<br />&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #0000BB">$arg&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #DD0000">'baz'</span><span style="color: #007700">;<br />&nbsp;&nbsp;&nbsp;&nbsp;echo&nbsp;</span><span style="color: #DD0000">'After&nbsp;change&nbsp;&nbsp;:&nbsp;'</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">var_export</span><span style="color: #007700">(</span><span style="color: #0000BB">func_get_arg</span><span style="color: #007700">(</span><span style="color: #0000BB">0</span><span style="color: #007700">)),&nbsp;</span><span style="color: #0000BB">PHP_EOL</span><span style="color: #007700">;<br />}<br /><br /></span><span style="color: #0000BB">$arg&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #DD0000">'bar'</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">byVal</span><span style="color: #007700">(</span><span style="color: #0000BB">$arg</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">byRef</span><span style="color: #007700">(</span><span style="color: #0000BB">$arg</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">?&gt;</span>
</span>
</pre></div>
    </div>

     <div class="example-contents"><p>以上例程会输出：</p></div>
    <div class="example-contents screen"><br />
As passed     : &#039;bar&#039;<br />
After change  : &#039;bar&#039;<br />
As passed     : &#039;bar&#039;<br />
After change  : &#039;baz&#039;<br />
    </div>
   </div>
  </p>

 </div>


 <div class="refsect1 notes" id="refsect1-function.func-get-arg-notes">
  <h3 class="title">注释</h3>
  <blockquote class="note"><p><strong class="note">Note</strong>: <p class="para">因为函数依赖于当前作用域以确定参数的细节，所以在
5.3.0 以前的版本中不能用作函数的参数。如必须传递此值时，可将结果赋与一个变量，然后用此变量进行传递。</p></p></blockquote>
  <blockquote class="note"><p><strong class="note">Note</strong>: <p class="para">如果参数以引用方式传递，函数对该参数的任何改变将在函数返回后保留。</p></p></blockquote>
  <blockquote class="note"><p><strong class="note">Note</strong>: 
   <span class="simpara">
    This function returns a copy of the passed arguments only, and does not
    account for default (non-passed) arguments.
   </span>
  </p></blockquote>
 </div>


 <div class="refsect1 seealso" id="refsect1-function.func-get-arg-seealso">
  <h3 class="title">参见</h3>
  <p class="para">
   <ul class="simplelist">
    <li class="member"><span class="function"><a href="func_get_args.html" class="function" rel="rdfs-seeAlso">func_get_args()</a> - 返回一个包含函数参数列表的数组</span></li>
    <li class="member"><span class="function"><a href="func_num_args.html" class="function" rel="rdfs-seeAlso">func_num_args()</a> - Returns the number of arguments passed to the function</span></li>
   </ul>
  </p>
 </div>


</div></div></div></body></html>